The Fischer-Tropsch process can be used for the conversion of hydrocarbonaceous feed stocks into liquid and/or solid hydrocarbons. The feed stock (e.g. natural gas, associated gas and/or coal-bed methane, coal) is converted in a first step into a mixture of hydrogen and carbon monoxide (this mixture is often referred to as synthesis gas or syngas). The synthesis gas is then converted in one or more steps over a suitable catalyst at elevated temperature and pressure into paraffinic compounds ranging from methane to high molecular weight molecules comprising up to 200 carbon atoms, or, under particular circumstances, even more.
Numerous types of reactor systems have been developed for carrying out the Fischer-Tropsch reaction. For example, Fischer-Tropsch reactor systems include fixed bed reactors, especially multi tubular fixed bed reactors, fluidized bed reactors, such as entrained fluidized bed reactors and fixed fluidized bed reactors, and slurry bed reactors such as three-phase slurry bubble columns and ebulated bed reactors.
The catalyst used in a (multi tubular) fixed bed Fischer-Tropsch reactor is often formed by extrusion. While this allows a variety of shapes to be made, the extrudate produced is limited and in practice only the cross section shape of the extrudate can be varied. Another limitation is the sizing of such particles. The optimum thickness of catalyst for fixed bed Fischer-Tropsch reactors is around 200 μm in view of diffusion limitations. However catalyst particles of such a thickness are too weak and break during reactor loading and cannot carry the weight of the reactor bed above.
The catalyst used in a fixed fluidized bed Fischer-Tropsch reactor often is a coated substrate, for example a coated metal substrate such as a coated metal sponge or a coated metal wire structure. The weight of a (metal) substrate and the loss of reactor space is a concern. In certain applications it would be desirable to have less space occupied by the substrate, and lower internal voidage to make optimal use of the reactor space.